Today's typical PBXs are essentially comprised of a collection of different types of Peripheral Equipment (PE) and a call processing applications all subtending from a single or hierarchical Time Division Multiplexing (TDM) switch. The types of PE typically found include those dedicated to line side access (i.e., telephone termination) support, trunk side access (i.e., network termination), and centralized, shareable resources such as conference bridges, echo cancellers, and Dual Tone Multi-Frequency (DTMF) receivers, to name a few. In each of these cases, all of them are rather tightly bundled together in terms of not only physical packaging, but more importantly, in terms of Operation and Management (OAM). The main function of a PBX being call processing, the relationship between it and each PE is “one-to-one”, “dedicated”, and “ownership-based”. Call processing not only maintains the state of calls, it also maintains the state of users, telephones, trunks, conference bridges, etc., and defines the usage paradigm. Telephone resources (e.g., keys, lamps, displays, speaker, etc.) and contention for them, are not managed by the phone itself, but rather by the call processing application subject to the same ownership paradigm. For example, any adjunct application such as a voice Mail (VM) can only access/control PBX and terminal resources indirectly through the call processing application, since it is the call processing application that ‘owns’ these resources, keeps state information for them, etc. Furthermore, a user trying to context select between an existing call and a call waiting or a call on hold, must interact with call processing rather than the terminal.
This model lacks flexibility and does not provide the opportunity to share the voice PE resources. A system providing these advantages would inherently give users enhanced services.